PCDD/Fs in fly ash from municipal solid waste incinerators (MSWIs) can be decomposed in non-thermal plasma, more in particular in a vortex-shaped gliding arc. Typical operating conditions are 10 kV voltage, 40 k Omega B external current-limited resistor, 11 L/min tangential gas and 2 L/min axial carrier gas flow rates. Degradation efficiencies of PCDD/Fs are respectively 54.9, 61.7 and 66.8 % on mass basis and 60.7, 73.3 and 70.1 % on toxicity basis under N-2, air and O-2 condition. After treatment the morphology of fly ash has changed: needle-shaped crystals increasing, pores and fragments appearing and high-temperature melting showing which is leaded by direct contact with high-temperature core of arc. The results are explained tentatively by the creation of reactive intermediates leading to dechlorination and oxidation of PCDD/Fs and finally producing end-products such as CO2, CO, HCl and CH4.